Patients With Underactive Thyroid Report Pervasive Brain Fog

Nearly half all patients with hypothyroidism reported experiencing “brain fog,” even before receiving a diagnosis, a researcher reported.

In an online survey of over 5,000 people with hypothyroidism, 905 (17.1%) said they experienced new-onset brain fog symptoms in the weeks or months following their initial diagnosis, according to Matthew Ettleson, MD, of the University of Chicago.

But 46% of all patients questioned said they experienced brain fog symptoms prior to receiving their hypothyroidism diagnosis, Ettleson explained in a presentation at the American Association of Clinical Endocrinology (AACE) virtual meeting.

The vast majority (82%) of these patients with brain fog symptoms said they experienced them frequently or all of the time.

In regard to hypothyroidism etiology, about half of those who reported these new brain fog symptoms after diagnosis had undergone thyroid surgery and/or radioactive iodine therapy (RAI) therapy. Another third had Hashimoto’s disease, and the latter was more common among the patients who experienced brain fog prior to their hypothyroidism diagnosis.

The top symptom reported regardless of hypothyroidism etiology was fatigue, marked by lack of energy or feeling sleepy. Other symptoms of hypothyroidism-related brain fog included forgetfulness, difficulty making decisions, and mental confusion, as well as anxiety and depressive symptoms.

Not surprisingly, most of the patients who experienced brain fog frequently or all of the time said it negatively affected their quality of life. The frequency of cognitive symptoms of brain fog tended to be the factor most strongly correlated to patients being unsatisfied, according to Ettleson and colleagues.

When seeking relief, more than half of patients said that rest and relaxation was one of their go-to strategies for coping with brain fog. Another 11% of respondents said exercise and outdoors time helped relieve their symptoms. A few said that dietary modification helped improve their symptoms, while gluten and a sugar-rich diet tended to worsen symptoms.

As for thyroid hormone medications, 14% said an adjustment of their thyroid medication helped alleviate some of their brain fog, while another 9% said liothyronine helped. Of note, more patients said levothyroxine worsened their brain fog.

The data was collected via an online survey to hypothyroidism support groups and the American Thyroid Association. The survey included 11 items with questions on etiology of hypothyroidism, age, sex, frequency of brain fog symptoms, type of symptoms, and onset of symptoms, as well as open-ended questions about what improves, or worsens, symptoms, and an explanation of what patients experience.

The majority of respondents were female with a mean age of about 49.

“My biggest takeaway in terms of practice is that for many of these patients, it may honestly have nothing to do with their thyroid,” said Ettleson. “We saw a large portion of patients that said they had symptoms well before they were ever diagnosed with hypothyroidism, and yet many of these patients have linked these brain fog symptoms to their thyroid. I think it’s sort of imperative to the clinician to at least engage in these conversations and not just stop once we’ve seen the thyroid function tests are normal.”

Given the findings of the study, physicians should consider discussing lifestyle changes with patients, along with thyroid hormone adjustment, he added.